Detachable electrical connectors are used to temporarily connect electronic components or accessories with electronic devices. Besides providing a low-resistance electrical connection, the electrical connectors must be mechanically stable to ensure a permanent electrical connection. The demands on the reliability of the electrical connections are of particular importance if the electronic devices are used under conditions where mechanical stress or load occurs. For such electronic devices, rugged electrical connectors are required.
A typical example of an electronic device, which may experience mechanical stress, is a mobile phone. Although specific accessories such as carrying cases are available for mobile phones to reduce the risk of mechanical stress, the mobile phone could still, for example, be accidentally dropped on a floor. The high mechanical stress of such an impact could lead to severe damage of the mobile phone.
A removable battery pack, which is detachably connected with the mobile phone, is a typical example of an electronic component. An example of such a battery pack is disclosed in U.S. Pat. No. 6,171,138 B1. This battery pack comprises an electrical connector assembly having a latch and a U-shaped contact housing. The contact housing accommodates a plurality of stacked electrical contacts. The latch, which is partially surrounded by the contact housing, engages with a housing of a mobile phone to fasten a battery cover. Each of the stacked electrical contacts comprises a non-compliant portion, which is fixed to the contact housing, and a compliant portion having a contact portion for contacting corresponding receptacle contacts of a receptacle connector fixed to the mobile phone. At the non-compliant portion, contact attachment tabs are provided, which are inserted into corresponding contact alignment slots of the contact housing. For further alignment, alignment slots are provided in walls of the contact housing. The compliant portions of the electrical contacts extend through the alignment slots so that the contact portions of the electrical contacts are exposed on an outside of the contact housing. When the battery cover is attached to the mobile phone, the contact portions are resiliently pressed against the receptacle contacts by the compliant portions of the stacked electrical contacts.
Another example of an electrical connector assembly for a battery pack of a mobile phone is disclosed in U.S. Patent Application Publication No. 2004/0002265 A1. This assembly comprises a base connector and a socket connector. The base connector is fixed onto a mounting surface by soldering. The socket connector is inserted into an insertion space of the base connector along a mating direction, which is substantially perpendicular to the mounting surface. Plate-like contacts are arranged in the insertion space and extend substantially parallel to each other. The plate-like contacts are contacted by contacts of the socket connector. Each of contacts includes a pair of contact pieces extending substantially parallel to each other. Each of the contact pieces is provided with a contact portion. The contact portions project toward each other and engage with side walls of the plate-like contacts of the base connector. The socket connector is further connected to a conductor, which generally extends parallel to the mounting surface of the base connector when the socket connector is inserted. The socket connector and the base connector further comprise cam surfaces angled with respect to the mounting surface of the base connector to convert tensions exerted on the socket connector into a substantially perpendicularly orientated force. As a consequence, when pulling on the leads, the engaging cam surfaces redirect the acting forces into extracting forces substantially perpendicular to the mounting surface to unplug the socket connector. Shear stresses within the solder joints between the base connector and the mounting surface are thereby partially reduced.
Mechanical strains of an electrical connection can also occur within stationary electronic devices and efforts have been made to compensate for the mechanical strains and to improve the reliability of the electrical connection. Stress compensation is of particular importance when the electrical contacts of the connectors are directly soldered to a printed circuit board. A contact element with improved stress-compensation is, for example, disclosed in U.S. Pat. No. 4,998,890. This contact element is used as an electrical connector for connecting a daughter board to a mother board. When soldered to a printed circuit board, the contact element extends substantially perpendicular to a main surface of the printed circuit board. The contact element comprises a base portion and first and second spring contact portions, which are supported by resilient supporting arm members integrally attached to the base portion and the spring contact portions. The first and second spring contact portions contact each other on a boundary separating line along which the spring contacts portions can slide with respect to each other to prevent overstress when the daughter board is inserted into the contact element.